const titleToNumber = str => {
    const map = {
        A: 1,
        B: 2,
        C: 3,
        D: 4,
        E: 5,
        F: 6,
        G: 7,
        H: 8,
        I: 9,
        J: 10,
        K: 11,
        L: 12,
        M: 13,
        N: 14,
        O: 15,
        P: 16,
        Q: 17,
        R: 18,
        S: 19,
        T: 20,
        U: 21,
        V: 22,
        W: 23,
        X: 24,
        Y: 25,
        Z: 26,
    };
    let res = 0;
    const len = str.length;
    for (let i = 0; i < len; i++) {
        // 根据map取得字母对应的数字
        res += map[str[i]] * 26 ** (len - i - 1);
    }
    return res;
};
